Method of producing electric heating pads



July 4, 1961 A. NEGRoMAN-rl 2,990,607

METHOD OF PRODUCING ELECTRIC HEATING PADS Filed May 31. 1955 UnitedStates Patent C) 2,990,607 MEIHOD F PRODUCING ELECTRIC HEATING PADSAntonio N egromanti, Via delle Forze Armate, Milan, Italy Filed May 31,1955, Ser. No. 512,095 Claims priority, application Great Britain June3, l1954 4 Claims. (Cl. 29-155.5)

This invention relates to an industrial method for the continuousproduction in indefinite lengths of multi-tubular strips of syntheticresins, adapted to receive bare heating resistances without any risk ofshort circuits, more particularly for the mass-production ofelectrically heated pads and blankets.

The method is applicable to any synthetic resin or other materialcapable of being welded either electronically or with simple heatedelectrodes, whether vit is produced in sheets or whether it constitutesthe coating of at least one surface of some other material, which initself is not weldable, such for instance as ordinary woven fabrics ofwool, silk or cotton.

The invention comprises the threading of the heating y circuits throughthe tubes either during or after the formation of the tubes.

Some advantageous methods of carrying out the invention are illustratedmerely by way of example in the accompanying drawings, in which:

FIGURE l is a diagrammatic plan view of apparatus for the preparation ofa multi-tubular strip, with tubes extending in the longitudinaldirection, wherein the resistance wires are introduced into the tubessubsequently to the formation of the latter;

FIGURE 2 shows multi-tubular zones without resistance wires;

FIGURE 3 shows one of the multi-tubular zones of FIGURE 2, now providedwith the resistance wire;

FIGURE 4 shows an electrode consisting of a metal cylinder;

FIGURE 5 is a diagrammatic plan -view of apparatus for introducing theresistance Wires into the tubes; during the formation of the same; and

FIGURE 6 shows the same apparatus in side elevation.

In FIGURE l, 1 denotes a table, at the opposite ends of which aremounted rotatable rollers 2 and 3. On the roller 2 are accurately woundtwo superposed strips of electronically weldable material, for instancea synthetic resin, or two strips of any textile fabric the adjacentsurfaces of which have been previously coated with a weldable material.3 is a drawing roller, which is actuated by a motor or by a crank 4, andupon which the composite strip 5 is wound after unwinding from theroller 2 and being passed between electrodes `6 and 7.

The lower electrode 6 is constituted by a metal roller, and the upperelectrode 7 consists of a shaft upon which are threaded rotatable metaldiscs 8 of equal diameters, suitably spaced apart and insulated from oneanother.

The electrodes 6 and 7 thus formed are connected with a commonelectronic generator designed for such welding. j

By rotating the crank 4 and energising the electrodesA 6 and 7, the twoelementary strips will be welded to one another throughout their lengthalong parallel lines corresponding to the discs 8.

If the current from the electronic generator is interrupted atpredetermined equal intervals, the strip will becomel composed of somany adjacent alternate multitubular zones alternating with zones devoidof welding, where the elementary strips will remain completely separatefrom one another, all the welds terminating upon one and the same linetransverse to the strips.

Assuming now that the even discs 8 are energised separately from the odddiscs 8, with a retard or an anticipation between the two groups. Inthis case the corresponding welds will terminate on two lines transverseto the strip instead of terminating all on the same line, lthe ends ofthe welds being staggered as shown by the lines on the strip representedin FIGURE 2.

Thus, assuming that it is desired to create multitubular zones of anydesired predetermined contours, and still with staggered welds, it willbe necessary to energise and de-energise the discs 8 separately from oneanother, and in the order required by the said contours.

FIGURE 3 shows one of the multi-tubular zones of FIGURE 2, now providedwith a resistance wire 9, which, owing to the staggered welds, `can beemployed bare without any risk of short circuits.

If it is desired to arrange the tubes in the direction of the breadth ofthe strip, all that is necessary is to put in place of the upperelectrode 7, the electrode of FIGURE 4, consisting of a metal roller 10rotatable upon a shaft 11, mounted parallel to the axis of the lowerelectrode 6. Along the lateral surface of the roller 10 are arranged,spaced part at will and in the direction of the generating lines,projections 12, staggered in relation to the ends of the said roller 10.Every time one of the projections 12 arrives against the electrode 6, aweld of the two elementary strips will be effected. In this case alsomulti-tubular zones of pre-determined contours can be produced.

In point of fact it will be suficient to use a roller 10 of suficientdiameter such that in a development of its peripheral surface on to aplane the projections 12 would follow with their ends the contours ofthe desired multitubular zone.

FIGURE 5 represents diagrammatically, as seen from above, the apparatusby means of which the introduction of resistance wires into the tubescan be effected simultaneously with the formation of the tubes.

FIGURE 6 shows the same apparatus as seen from the side.

In these figures, 13 denotes a table, at the two opposite ends of whichare mounted rotatable rollers 14 and 15, upon which the two elementarystrips of weldable material 16 `and 17 are wound separately, and fromwhich they are guided towards the centre of the table, where drawingrollers 18 and 19, constantly pressed against the strips incorrespondence with their ends, periodically occasion an advance of thesaid strips, the advance being adjustable at will and equal to thedistance between two successive welds. By means of a suitable cam, notshown, which works synchronously with the rollers 18 and 19, twoelectrodes 20 and 21 connected to the electronic generator are movedtowards and away from the strips, and are at the same time energised andde-energised. A second cam, also not shown, occasions, at the end ofeach weld, a displacement of the electrode 21 to right and leftalternately in relation to the electrode 20, in order to have the weldsstaggered as in the oase previously described. The resistance wire,wound upon a stationary bobbin 22, is by means of the arm 23 set downgently between the two strips 16 and 17 parallel to and in proximity toeach weld. The arm 23, by means of a suitable cam, not shown,accomplishes alternate angular displacements to the right and to theleft, n such `a way that to eachV of these displacements therecorresponds the setting of a length of resistance wire equal to thelength of a weld. These displacements also are synchronised in relationto the electrodes 20 and 21 and to the rollers 18 and 19.

More specifically, a motor of suitably reduced speed causes the drawingrollers 18 and 19 to accomplish a first angular rotation correspondingto the desired advance of the elementary strips 16 and 17, or equal tothe desired distance between two succesive welds, after which the saidrollers undergo a stoppage. The electrodes 20 and 21 Aare -then pressedagainst one another, and are thereby energised for the time necessaryfor effecting a first weld, simultaneously with which weld the settingwill occur of a iirst length of resistance wire by means of the arm V23.There will follow the removal of the electrodes 20 and 21, previous toltheir de-energising, and then there will be another angular rotation ofthe rollers 18 and V19, which will be followed by the operationsindicated above, in the order already indicated, it being noted that theelectrode 21 is pressed against the electrode 20, once displaced towardsone side of the two strips 16 and 17, and the next time displacedtowards the opposite side of the two strips, thereby having the weldsstaggered, as in the preceding cases.

This will give rise to a multi-tubular strip already provided withresistance wire, which, when cut to the desired length, incorrespondence with two welds, will furnish so many pads or blankets,which will be completed by the addition of current-supply wires and aiinishing marginal weld. Such a strip can be rolled up on a roller Z4,frictionally actuated by the motor on which all the other movementsdescribed above depend.

For the sake of simplicity the various cams on which the abovementionedoperations depend have 'not been indicated, since it would be easy for acompetent expert to design various arrangements thereof which 'would beadapted to give rise to the requisite movements in the order indicatedabove.

I claim:

l. A method of producing electrically heatable flexible appliances suchas pads and blankets, comprising the steps of: placing two strips `offany electrically insulating fabric or other exible material, of the samewidth and of indenite length, in contact with one another, Vsaid stripsboth consisting, at least as regards their adjacent surfaces, ofmaterials such as synthetic resins which are capable of being welded,passing said two strips in contact with one another between electrodesadapted to weld them together along groups of parallel lines, alternatelines terminating inwardly of the ends of lines adjacent thereto, theends of all said lines being spaced from the outlines of said appliancesto be produced, at the same time energizing said said electrodes andthereby welding Said two strips together along said lines to provide atubular space between adjacent lines; severing the composite strip thusformed into units by transverse cuts between the successive groups ofwelded lines and inserting a bare electrical resistance wire freely andremovably through all the tubular spaces formed between said weldedlines in each unit, said wire passing from one tubular space to the nextaround the end of the welding line which terminates inwardly of theadjacent ends of the adjacent welding lines, welding said two strips ofeach unit to one another along the periphery, and attaching insulatedcurrentsupply wires to the ends of said resistance wire of each unit.

2. A method of producing electrically heatable appliances such as padsand blankets, comprising the steps of: passing two superposed strips ofany electrically insulating fabric or other iiexible material, of thesame width and of indeiinite length, consisting, at least as regardstheir adjacent surfaces, of materials such as'synthetic resins which arecapable of being welded, in contact with one another between electrodesadapted to weld said two strips together along vgroups of parallel linesextending in the longitudinal direction of said strips, alternate linesin each group terminating inwardly of the ends of lines'adjacent theretoand the length of said lines in each group being somewhat less than thelength of said unit pad or blanket to be produced, at the same timeenergizing-said electrodes and thereby welding the two strips togetheralong said lines to provide a tubularrspace between adjacent lines,severing the composite strip thus formed .into `unit appliances bytransverse cuts between said successive groups of welded lines,inserting a bare electrical resistance wire freely and removably throughall the tubular spaces formed between said welded lines in each unit,said wire passing from one tubular space to the nex-t around said end ofthe welding line which terminates inwardly of the adjacent end of theadjacent welding lines, welding the edges of each unit appliancetogether all round the periphery of the unr't, `and attaching insulatedcurrent-supply wires'to said ends of the resistance wire of eachappliance.

3. A method of -producing electrically heatable appliances-such as padsand blankets, comprising the steps of: passing two superposed strips ofany electrically insulating fabric or other Yiiexible material, of thesame width and of indefinite length, consisting, at least as regardstheir adjacent surfaces, of materials such as synthetic resins which arecapable of being welded, in contact with one another between electrodesadapted to weld the two strips together along groups of parallel linesextending in the transverse direction of said strips, alternate lines ineach group terminating inwardly of the ends of lines adjacent thereto,the length of said lines in each group being somewhat less than thelength of the unit appliance to be produced, at the same time energizingthe electrodes and thereby welding the two strips together along thesaid lines to provide a tubular space between adjacent lines, severingthe composite strip thus formed into unit appliances by transverse cutsbetween said successive groups of welded lines, inserting a bareelectrical resistance wire freely and removably through all said tubularspaces formed between said welded lines in each unit, said wire passingfrom one tubular space to the next around the end of said welding linewhich terminates inwardly of the adjacent ends of the adjacent weldinglines, welding the edges of each unit pad or blanket together all roundthe periphery of the unit appliance, and attaching insulatedcurrent-supply wires to the ends of the resistance wire of each unitappliance.

4. A method of producing electrically heatable applances such as padsand blankets, of any electrically insulating fabric or other flexiblematerial, of the same width and of indefinite length, both consisting,at least as regards their adjacent surfaces, of materials such assynthetic resins which are capable of being welded, comprising the stepsof passing said two strips in contact with one another betweenelectrodes adapted to weld said two strips together along groups ofparallel lines extending in the transverse direction of said strips,alternate lines in each group terminating inwardly of the ends of linesadjacent thereto, the length of said lines in each group being somewhatless'than the width of said strips, at the same time energizing theelectrodes and thereby welding said two strips together along saidlines, inserting a bare electrical resistance wire Ifreely and removablythrough all the tubular spaces thus formed in each unit between thewelded lines, said wire passing ifrom one tubular space to the nextaround the end of the welding line which terminates inwardly of theadjacent ends of adjacent welding lines, severing the composite stripthus Vformed into unit appliances by transverse cuts between thesuccessive groups of welding lines, welding the edges of each pad orblanket together all round the periphery, and attaching insulatedcurrent-supply wires to the ends of the resistance wire of each unitappliance.

References Cited in the iile of this patent UNITED STATES PATENTS1,564,681 Kercher Dec. 8, 1925 2,493,968 Hepner Jan. l0, 1950 2,548,467Crise Apr. l0, 1951 2,548,468 Crise Apr. 10, 1951 2,621,139 Messing Dec.9, 1952 2,757,273 Taylor July 31, 1956 '2,774,051 f McCarthy Dec. 11,1956

